Characterization of rice husk-based catalyst prepared via conventional and microwave carbonisation

© 2017 Elsevier Ltd. Carbon-based sulphonated catalysts (CBSCs) were made from rice husk for biodiesel production. The CBSCs were prepared by microwave (MW) and conventional heating processes from the same feedstock. In both heating systems, the preparation was a two-step process: carbonisation and sulphonation. The aim of this study was to use MW heating to reduce the conventional CBSC preparation time and enhance the -SO 3 H group attachment to the solid catalyst. The biomass based solid acid catalysts from the two systems were characterised and compared in terms of physicochemical properties including: sulphonation, morphology, surface area and structure. The reaction times for MW assisted carbonisation and for sulphonation were significantly reduced compared to the conventional heating system; these were 30 min vs 4 h and 20 min vs 12 h, respectively. The MW prepared catalyst showed higher sulphur content (4.91%) as compared to the conventional catalyst (2.10%). The FTIR analysis showed well distinguished peaks for -SO 3 H for the MW prepared catalyst suggesting the solid catalyst was successfully sulphonated, while these peaks were very weak for the conventional catalyst. SEM analysis revealed a highly porous structure in the MW prepared catalyst, whilst a denser solid resulted for its conventionally prepared analogue, owing to the higher temperatures applied and longer sulphonation time. The surface area for the MW was higher than the conventionally prepared catalysts (43.63 m 2 /g and 37.01 m 2 /g, respectively). The structure of the samples was identified as amorphous for both catalysts as confirmed by XRD. The prepared CBSC is expected to catalyse biodiesel production reaction as evidenced by its total acidity and surface area

Liquid digestate recycled utilization in anaerobic digestion of pig manure: effect on methane production, system stability and heavy metal mobilization

To improve bioenergy, methane, production in the anaerobic digestion plant application, the effects of recycled liquid digestate on anaerobic digestion of pig manure were investigated. Two continuous stirred tank reactors were operated for 230 days with varying organic loading rates (OLRs, from 1.5 to 6 g VS L-1 d-1); one reactor was implemented with liquid digestate recirculation and the other was set as the control without recirculation. It was demonstrated that the recirculation operation improved methane production and system fermentation stability, particularly for OLRs below 5 g VS L-1 d-1. The inhibition of methane production was found under an OLR of 6 VS L-1 d-1, which was caused by significantly increased viscosity from 30 to 1000 mPa·s and decreased mass transfer characteristics. The previously reported negative effects of accumulated ammonia and VFA on anaerobic digestion under digestate recirculation were not found in the present investigation of pig manure treatment. However, the heavy metals Pb, Mn, Cu and Zn accumulated in both liquid and solid fractions of the generated digestate in the digestate recycled reactor. The stable carbon isotope analysis of δ13CCO2 and δ13CCH4 produced the biogas may indicate different methanogenic pathways between the anaerobic reactors with and without digestate recirculation

Hydrolysis of oligosaccharides over solid acid catalysts: a review

Mild fractionation/pretreatment processes are becoming the most preferred choices for biomass processing within the biorefinery framework. To further explore their advantages, new developments are needed, especially to increase the extent of the hydrolysis of poly- and oligosaccharides. A possible way forward is the use of solid acid catalysts that may overcome many current drawbacks of other common methods. In this Review, the advantages and limitations of the use of heterogeneous catalysis for the main groups of solid acid catalysts (zeolites, resins, carbon materials, clays, silicas, and other oxides) and their relation to the hydrolysis of model soluble disaccharides and soluble poly- and oligosaccharides are presented and discussed. Special attention is given to the hydrolysis of hemicelluloses and hemicellulose-derived saccharides into monosaccharides, the impact on process performance of potential catalyst poisons originating from biomass and biomass hydrolysates (e.g., proteins, mineral ions, etc.). The data clearly point out the need for studying hemicelluloses in natura rather than in model compound solutions that do not retain the relevant factors influencing process performance. Furthermore, the desirable traits that solid acid catalysts must possess for the efficient hemicellulose hydrolysis are also presented and discussed with regard to the design of new catalysts

Biomethanation potential of biological and other wastes

Anaerobic technology has been traditionally applied for the treatment of carbon rich wastewater and organic residues. Anaerobic processes can be fully integrated in the biobased economy concept for resource recovery. After a brief introduction about applications of anaerobic processes to industrial wastewater treatment, agriculture feedstock and organic fraction of municipal solid waste, the position of anaerobic processes in biorefinery concepts is presented. Integration of anaerobic digestion with these processes can help in the maximisation of the economic value of the biomass used, while reducing the waste streams produced and mitigating greenhouse gases emissions. Besides the integration of biogas in the existing full-scale bioethanol and biodiesel production processes, the potential applications of biogas in the second generation lignocellulosic, algae and syngas-based biorefinery platforms are discussed.(undefined